Tyre Shops sending undamaged tyres for recycling without asking customer?

[werner]

Yeah. Tell that to the acquaintance who had her X6 go into "limp" mode when it detected the circumference of the left rear tyre is not the same as the right rear tyre.

Only 5000km difference between them, but she had to replace both.

and logically speaking, as we are on a technology forum, how would you program a sensor to do what you claimed it did?

 

[thehuman]

Easy . If left and right wheel amount of rotations not the same for a set kilometres of travel

 

[SauRoNZA]

Slightly off topic, but why didn't you only replace the damaged tyre? I know some people say all your tyres have to be the same brand and condition but that's bollocks.

It's not so much about the brand as it is the tread pattern causing the tyres to "fight" each other and more rolling resistance from one over another which could mean that it affects your wheel alignment etc.

As was said above the wear could also cause a difference to the speed sensors which would cause the ESC/STM/SMP not to work properly or as was mentioned above to even cause a warning.

Last thing you want is for the safety net to cause the accident when you are in a pickle.

 

[SauRoNZA]

and logically speaking, as we are on a technology forum, how would you program a sensor to do what you claimed it did?

You don't program anything.

The sensor gets a different reading from either side because of the minor size difference in tyres.

The ESP system which normally compensates for a sudden change in rotation speed now gets confused because it's constantly getting a dodgy reading and therefore puts the car into safe mode.

 

[werner]

You don't program anything.

The sensor gets a different reading from either side because of the minor size difference in tyres.

The ESP system which normally compensates for a sudden change in rotation speed now gets confused because it's constantly getting a dodgy reading and therefore puts the car into safe mode.

yes, thats the simple answer. But we're on higher grade logic here. Where we can see the flaws in the simple answers.
Of course, cars dont often drive in a straight line, so one wheel is always going a different speed to the other. Hello differentials.
So given time (e.g. one day of driving), you will not find a 2 second piece of data when you can reliably say one wheel is bigger than the other. Even if you measure steering angle at that point in time.
So I still call bull****
The sensor may well say one wheel is 1mm smaller than the other, but it had no way of knowing you werent just doing 120km/h on the highway on a very very gentle bend. Or that you just hit a patch of dirt with one wheel while pulling off, spinning one wheel 2 times more than the other.
So you have no reliable data to work from.

Ok, lets try it with all 4 wheels, and try solve for the smallest/incorrect wheel.
Any ideas on how we can do this?
Problem here is...damn ice/gravel/snow making all wheels spin at different speeds at any given moment, throwing all our lovely careful laboratory observations out of the window.
So for a dire dire situation where limp home mode is called for (that is a dire situation, isnt it? the vehicle is trying to protect itself), we would need some data that we can seriously rely on, in all situations. I cannot see a source of data to work from that is reliable enough to detect one tyre being slightly smaller than the other (...we're not talking diffent inches, or a different profile...the chap was talking about 5000km of wear. Which will be about half a millimetre)

Iemand praat ***.


edit: just realised my tone sounds confrontational, whereas that isnt how I feel when writing this. I'm trying to open a discussion on how this can be achieved, imagine we are all at bootcamp for bmw and they come up with this problem and ask for a way to detect it
cool

 

[Ockie]

Not if they put up a sign in a conspicious place advising of this policy.

I am going to put up a sign in our store in a obscure place...you upgrade, your old phone is ours, broken or not.....and we will give you a hidden R80.00 discount on your new phone that does not actually reflect anywhere. Thanks for your business.

 

[IzZzy]

Not sure your point here. The sign imposes contractual terms on a party seeking to do business - often it relates to exclusion of liability or indemnities. The law on imposed terms is not certain - but generally if the sign is in a place where a potential customer can see (and read) it before consumating any transaction, then the terms are usually imposed.

You are free to do business on the terms imposed or not at all.

 

[SauRoNZA]

yes, thats the simple answer. But we're on higher grade logic here. Where we can see the flaws in the simple answers.
Of course, cars dont often drive in a straight line, so one wheel is always going a different speed to the other. Hello differentials.
So given time (e.g. one day of driving), you will not find a 2 second piece of data when you can reliably say one wheel is bigger than the other. Even if you measure steering angle at that point in time.
So I still call bull****
The sensor may well say one wheel is 1mm smaller than the other, but it had no way of knowing you werent just doing 120km/h on the highway on a very very gentle bend. Or that you just hit a patch of dirt with one wheel while pulling off, spinning one wheel 2 times more than the other.
So you have no reliable data to work from.

Ok, lets try it with all 4 wheels, and try solve for the smallest/incorrect wheel.
Any ideas on how we can do this?
Problem here is...damn ice/gravel/snow making all wheels spin at different speeds at any given moment, throwing all our lovely careful laboratory observations out of the window.
So for a dire dire situation where limp home mode is called for (that is a dire situation, isnt it? the vehicle is trying to protect itself), we would need some data that we can seriously rely on, in all situations. I cannot see a source of data to work from that is reliable enough to detect one tyre being slightly smaller than the other (...we're not talking diffent inches, or a different profile...the chap was talking about 5000km of wear. Which will be about half a millimetre)

Iemand praat ***.


edit: just realised my tone sounds confrontational, whereas that isnt how I feel when writing this. I'm trying to open a discussion on how this can be achieved, imagine we are all at bootcamp for bmw and they come up with this problem and ask for a way to detect it
cool

You have completely disregarded all the other sensors involved in this system, especially the gyro/yaw one.

If that says the car is travelling in a straight line and all the wheels should be doing the same speed, but they are not...then obviously it should throw an error.

And as you say you need reliable data to work from, so if any of the huge numbers of sensors involved here are causing for incorrect data to be introduced then it makes sense the system would fail to safe mode.

*****

However I agree with you on the principle that minor tread wear (at 5000km) shouldn't be causing this.

Fitting a whole different wheel size though...that should fail instantly.

 

[Sepeng]

yes, thats the simple answer. But we're on higher grade logic here. Where we can see the flaws in the simple answers.
Of course, cars dont often drive in a straight line, so one wheel is always going a different speed to the other. Hello differentials.
So given time (e.g. one day of driving), you will not find a 2 second piece of data when you can reliably say one wheel is bigger than the other. Even if you measure steering angle at that point in time.
So I still call bull****
The sensor may well say one wheel is 1mm smaller than the other, but it had no way of knowing you werent just doing 120km/h on the highway on a very very gentle bend. Or that you just hit a patch of dirt with one wheel while pulling off, spinning one wheel 2 times more than the other.
So you have no reliable data to work from.

Ok, lets try it with all 4 wheels, and try solve for the smallest/incorrect wheel.
Any ideas on how we can do this?
Problem here is...damn ice/gravel/snow making all wheels spin at different speeds at any given moment, throwing all our lovely careful laboratory observations out of the window.
So for a dire dire situation where limp home mode is called for (that is a dire situation, isnt it? the vehicle is trying to protect itself), we would need some data that we can seriously rely on, in all situations. I cannot see a source of data to work from that is reliable enough to detect one tyre being slightly smaller than the other (...we're not talking diffent inches, or a different profile...the chap was talking about 5000km of wear. Which will be about half a millimetre)

Iemand praat ***.


edit: just realised my tone sounds confrontational, whereas that isnt how I feel when writing this. I'm trying to open a discussion on how this can be achieved, imagine we are all at bootcamp for bmw and they come up with this problem and ask for a way to detect it
cool

Similiar to how flat tyre sensors work isn't it? You get two types if memory serves - the ones where they measure the air pressures, the others that look at wheel speeds etc to determine if one wheels pressure is lower than the others. So it's definitely possible and happening, someone much smarter than me would be able to explain in detail.

 

[SauRoNZA]

Not sure your point here. The sign imposes contractual terms on a party seeking to do business - often it relates to exclusion of liability or indemnities. The law on imposed terms is not certain - but generally if the sign is in a place where a potential customer can see (and read) it before consumating any transaction, then the terms are usually imposed.

You are free to do business on the terms imposed or not at all.

Last i checked you can't just impose terms based on a random sign hidden somewhere in a shop.

Or at least any time this kind of thing has gone to court it's been thrown out.

 

[wetkit]

Ok, so i'm confused here, help me out.
You had a HUGE flat, went to the shop to get it fixed.
According to you the tyre is undamadged? How did it then get flat.
The shop puts a brand new tyre on, do not ask your permission for this, but you pay anyway?
Now you looking for the old tyre back?
Why did they not just patch your undamadged tyre then? A plug would do the trick!!

 

[werner]

I've havent heard of the second type, and if it did rely on wheels speeds then it will show incorrect pressures if you change your tyre/rim sizes (and you would read about that online, even on this forum)
"hey guys I just recently put on different rims and now my tyre pressure are all reading wrong by the same amount".....you'll need to stick an offset into the ecu to compensate.
Ever heard of that? I havent. Doesnt mean it exists, but if it does it isnt common.
And if it can work, then they would be using it, as speed sensors are already part of abs systems, so you could just simply add some more code and use that to measure tyre pressures, if it could do that. Cuts down costs. In which case, you'd be hearing about it when people change rims etc. But you dont.

My point is, if you were in the boardroom at a car manufacturer and some techie says he can use wheel speed sensors to measure and detect incorrect tyre wear
you would say "and then?"
and he says "we throw a limp code"
and you would say "gtfo"

I have never ever ever ever had 4 tyres replaced because they are all worn by the same amount. Never guys. Just think about it for a bit, and decide if putting a car in limp home mode due to the wear of 5000km of driving difference is the appropriate action. (estimated life 60000km...5000km is a miniscule amount wear.)


I've got faith the reported incident is true, in that the car was in limp mode, they did put 2 new tyres and, and the code got cleared.
I have no faith they are correlated.


math time (I know...boring)
x6 rear tyres...vaires.but seems
315/30/20 is used
rolling circumference=2287mm

diameter is 727mm
radius is half that, 364~ish mm

so lets wear on tyre down by 2mm.
our radius is now 362mm
diameter is now 723mm
rolling circumference is 2274mm
thats 99.4% of the original size.

so we need to reliably detect a 0.5% difference of 4 wheels spinning at different speeds (thats for a fairly oddly worn tyre...2mm difference in tread height compared to its friends), and going by our 0.5% difference we're going to throw a limp code?

and what about it Piet is particularly fat, and sits in the front right seat (just a random seat position), and nothing is wrong with the car at all, so that tyre now gets extra load, so while we are there we'll put the car in limp mode and throw an incorrect pressure code while we are at it.

It just doesnt stack up.

 

[ToxicBunny]

Ok, so i'm confused here, help me out.
You had a HUGE flat, went to the shop to get it fixed.
According to you the tyre is undamadged? How did it then get flat.
The shop puts a brand new tyre on, do not ask your permission for this, but you pay anyway?
Now you looking for the old tyre back?
Why did they not just patch your undamadged tyre then? A plug would do the trick!!

2 tyres... not just 1.

 

[werner]

Ok, so i'm confused here, help me out.
You had a HUGE flat, went to the shop to get it fixed.
According to you the tyre is undamadged? How did it then get flat.
The shop puts a brand new tyre on, do not ask your permission for this, but you pay anyway?
Now you looking for the old tyre back?
Why did they not just patch your undamadged tyre then? A plug would do the trick!!

he replaced the tyres as a pair.
one damaged and one undamaged.
to get a matchign set.

nobody likes odd socks

 

[wetkit]

Ha, ok, got it now.
Well, normally you check your spare at this stage and decide which one is the best.
Your old spare or your "new" spare.
Then chuck the oldest. What you going to do with it? Make a swing?

 

[Ockie]

Ok, so i'm confused here, help me out.
You had a HUGE flat, went to the shop to get it fixed.
According to you the tyre is undamadged? How did it then get flat.
The shop puts a brand new tyre on, do not ask your permission for this, but you pay anyway?
Now you looking for the old tyre back?
Why did they not just patch your undamadged tyre then? A plug would do the trick!!

The one tyre was badly damaged. But I had both replaced. I do not believe having a brand new tyre on the one side and a old one (even if the tread is still very much fine) on the other side. They took the other tyre also which was fine.

 

[Ockie]

Ha, ok, got it now.
Well, normally you check your spare at this stage and decide which one is the best.
Your old spare or your "new" spare.
Then chuck the oldest. What you going to do with it? Make a swing?

I dont have a spare. I would have liked to use this one as a spare

 

[Sepeng]

I've havent heard of the second type, and if it did rely on wheels speeds then it will show incorrect pressures if you change your tyre/rim sizes (and you would read about that online, even on this forum)

Hi,

got the below from Wiki. Knew there was something like this.

"Indirect TPMS[edit]


Indirect TPMS do not use physical pressure sensors but measure air pressures by monitoring individual wheel rotational speeds and other signals available outside of the tire itself. First generation iTPMS systems are based on the principle that under-inflated tires have a slightly smaller diameter (and hence higher angular velocity) than a correctly inflated one. These differences are measurable through the wheel speed sensors of ABS/ESC systems. Second generation iTPMS can also detect simultaneous under-inflation in up to all four tires using spectrum analysis of individual wheels, which can be realized in software using advanced signal processing techniques. The spectrum analysis is based on the principle that certain eigenforms and frequencies of the tire/wheel assembly are highly sensitive to the inflation pressure. These oscillations can hence be monitored through advanced signal processing of the wheel speed signals. Current[when?] iTPMS consist of software modules being integrated into the ABS/ESC units.
"
So these types of monitoring systems are in place - how exactly they work I'm afraid I won't be of much use.

 

[werner]

interesting, thank you for sharing this. I've learned something today. I'd love to find out how reliable it is..off to google, cheers!

 

[Colin62]

Iemand praat ***.

I agree

I've havent heard of the second type...

And I think I've found the culprit.

..off to google, cheers!

Good idea...